[nullc]

Not a shame: At least so far as has been envisioned proof-of-stake doesn't appear to actually work. The fundamental problem with proof of stake is that there is nothing at stake: Its in your rational best interest to mine all possible subchains that you can mine in, and not only in the single unique chain you believe to be most likely to survive, as is the case for PoW.

PPCoin's security is not provided by proof of stake but by cryptographically signed lockins broadcast to the network by its creator... so you have to trust this anonymous party to behave honestly. It sort of defeats the purpose of having a cryptocurrency.

Ripple is even worse in that regard— an opaque ledger implemented via a closed source system.

[yebyen]

I think you are wrong in this.

The source is open, you can build your own chain separate from PPC with the same (or incompatible algorithms), and there is plenty at stake; you might not think your chain will ever be long enough to win, but maybe your transactions need to be private and then there's that at stake.

It is impossible for me to imagine mining all possible subchains that you can mine in; maybe it's because there is no pool I know who supports merged mining in more than just BTC and NameCoin, but I thought there was a technical reason why it wasn't possible (or especially why it was possible specifically for this pair).

You can mine TerraCoin and PPCoin today when you don't need those hashes for BTC, but you can't mine all three at once.

So, how do you propose to mine all possible subchains that you can mine in for the PPC Proof of Stake coin? When the difficulty drops on one chain, it would be to your benefit to mine just that one chain, if you think it will be accepted as the longest chain. Unless you have BTGuild on your side, you don't have much hope of making the longest chain, unless you found a chain that they just forgot.

When I read the CDF graph, I got the impression there is a sweet spot for payouts on chains that behave according to CDF (and because of the nature of "averages" most of us don't have it yet and never will.)

You sound like a person who knows, so I hope you'll tell me more, since I'm interested in Proof-of-Work as it applies to PPCoin. I like the PPCoin website and if that's any indicator, I think that some people will pick PPCoin over Bitcoin without any technical expertise even if it only "seems fairer".

So, will you tell me more of what you know?

[vbuterin]

Altruism and defaults are powerful things. In fact, they're the only thing enforcing rules about "nonstandard transactions", without which the blockchain would have been DDoSed all the way to a terabyte by now.

And the checkpointing system is a backup measure used to maintain stability because PPCoin is still small; it is not intended to be the primary mechanism holding it up. If you want to see an altcoin without checkpoints, look at any of the ones that got killed by a 51% attack.